A Light-Emitting Diode (LED) can be an excitation source for optically transduced assays, such as fluorescent measurements. The need for providing an LED excitation beam source that does not exhibit excitation beam intensity changes and/or an excitation beam spectral shift has not been satisfied. A device compatible with nucleotide amplification reactions, detecting such reactions, and capable of processing a relatively large number of amplification reactions is desirable. A device capable of providing enhanced scanning, such as enhanced scanning speed and enhanced scanning methods, of multiple reactions or samples is also desirable.